1. Field of the Invention
The present invention relates to a network system for constructing a home network environment, and more particularly, to a data transfer control device, a relay device, and a control device suitable for use in the home network environment.
2. Description of the Background Art
In recent years, there is a rapid trend for digitalizing electronic instruments as exemplified by the term “multi-media”, and this trend is already noticeable in the office environment.
More specifically, in terms of hardware, this trend has been materialized in forms of introduction of PCs, digitalization of OA devices and formation of networks among them. Also, in terms of software, this trend has been expanding to cover the basic functions of hosts (which are progressively light-sized and transferred to PCs), the application software such as the word-processing software, the spreadsheet software, etc., and the Internet application such as the WWW.
The similar trend can also be seen in the home environment. Namely, even in the home environment, this trend for digitalization has been steadily progressed in forms of digitalization of AV devices (DVD, digital VTR, digital video camera, etc.), digitalization of broadcasting, and Internet access such as OCN.
Similarly as in a case of the office environment, this trend is expected to progress toward the formation of networks in future. Namely, it is expected that the technologies of various fields such as information processing, communication and broadcasting will be unified by the digitalization, and inter-mixed with each other by the formation of networks.
There are many candidates for the network technologies in this direction. For example, the Ethernet has overwhelming records of the actual use in the office environment and is probably the most promising candidate even for the home PC network. Also, the ATM is another serious contender because of the general consensus among the infra-structure constructors (telephone companies, CATV companies, etc.) to keep constructing the infra-structures based on this technology in view of the advantageous characteristics of the ATM such as its fast, real-time, and wide bandwidth properties.
In addition to these candidates, the network technology (bus technology) called IEEE 1394 has been attracting much attention recently. This IEEE 1394 has several remarkable characteristics such as its fast, real-time (QOS guaranteed), and plug-and-play properties, so that there is a high expectation especially among the AV industries on the IEEE 1394 as the most promising candidate for a future scheme for inter-connecting digital AV devices. This vogue has also instigated much interests to the IEEE 1394 from the computer industries as well.
In the initial phase, it is expected that the inter-connection of the home use digital devices will be realized by these various network technologies in conjunction with the spread of the home use digital devices, depending on preferences and demands of the users, and in this way prototype digital networks will be gradually built up inside each home.
In the second phase, there will be demands for inter-connecting these digital networks together. For example, there will be a desire to inter-connect an AV device connected to the 1394 network of a guest room on the first floor with another AV device connected to the 1394 network of a private room on the second floor in order to realize the dubbing or the cooperative operation between these AV devices.
However, in order to meet the expected demands of this second phase, the following problems must be addressed and resolved.
For now, it is highly likely that many AV devices will appear as dedicated 1394 terminals. This is because the infra-structures such as the Internet and B-ISDN are not yet fully developed so far so that it is presently rather difficult to develop any AV device that presupposes the availability of these infra-structures.
On the other hand, as these infra-structures come to be fully developed, it is expected that AV devices compatible with the Internet or B-ISDN will appear, but then it would be difficult to inter-connect such AV devices with the by then existing dedicated 1394 terminals. In addition, in such a case, only those terminals which are connected to the same 1394 as the dedicated 1394 AV devices would be capable of exchanging AV data and it would be impossible to exchange data with nodes which are connected to networks other than 1394 or nodes which are far distanced.